Question

Why is it beneficial for a leech to be able to store blood for months and release it slowly?

Answer 1

The reasons are:
- the blood is very low on nutrition
- the leech is not feeding itself regularly

The leech slows it metabolism a lot, so it can survive on very low nutrition. The blood is very low on nutrition, and it is the leech's food source, so the evolution made it preserve energy.

The leach doesn't have the opportunity to feed itself on regular basis, so it takes maximum advantage of any opportunity and consumes as much blood as possible so that it can survive long term when it will not have food at disposal.